Improving the efficiency of perovskite solar cells through optimization of the CH3NH3PbI3 film growth in solution process method

Perovskite-structured organic–inorganic materials such as CH 3 NH 3 PbI 3 are attracting much interest in the scientific community because of their abilities to function as revolutionary light harvesters and charge transfer materials for solar cells. To achieve high power conversion efficiency (PCE), it is critical to optimize the perovskite film layer. This paper reports the temperature and concentration controls on the two-step solution process. A diffusion-controlled growth mechanism is proposed for this process in tuning the morphology and purity of the perovskite film, which are proven to be important factors contributing to the photovoltaic performance. The highest PCE of 11.92% is achieved with an optimized perovskite crystal size of ∼150   nm and an appropriate amount of residual PbI 2 . This study sheds light on the design and fabrication of highly efficient, low-cost, solution-processed perovskite solar cells.